1. Field of the Invention
This invention relates to circuit breakers, and more particularly, to current limiting circuit breakers having a series double break contact system with at least two arc extinguishing chambers for each pole.
2. Description of the Prior Art
Recent trends in electrical distribution systems have involved increases in size and capacity to meet expanding demands for electrical service. For example, utilities have employed lower-impedance transformers to reduce power losses, regulation problems, and cost. Current-limiting circuit breakers are available with ratings up to 400A and interrupting capacities up to 200,000A.
To prevent such high available fault currents from damaging electrical distribution systems, protective devices limiting the prospective let-through currents are required. Fuses and, more recently, current-limiting circuit breakers have been used successfully to limit these high currents. They can reduce to tolerable levels both the peak fault currents (I.sub.p) and the thermal energy (I.sup.2 t) that reach downstream equipment. Mechanical and magnetic forces that can destroy equipment are proportional to the square of the peak currents (I.sub.p).sup.2, and thermal damage is proportional to the energy let-through.